There are several types of servo-assisted steering devices and systems known in the prior art and they all are structured to reduce the resistance of the control member when manoeuvring, regardless of the type of vehicle. The manoeuvring is enhanced by increasing the steering force acting on the control means, which generally is achieved by energizing an electric motor that for example can act in combination with a pump, in order to increase the pressure of the fluid flowing into the steering circuit.
The use of an electric motor within steering devices has the drawback of increasing the electric energy consumption that, if reaching high levels, affects the vehicle battery too much, causing the charge thereof to be exhausted.
This drawback is particularly significant above all for boats, since the exhaustion of the battery charge causes the boat to stop, thus running the risk of remaining stopped during voyage, far away from the coast and in uncomfortable conditions.
This drawback is an important problem of steering devices, since an excessive consumption of the battery charge does not allow vehicles to be started and/or to be normally operated, above all the ones where the electronic part has a high importance, such to particularly affect the battery charge.
In particular, if specific arrangements are not provided, when the motor of the vehicle reduces the supplied power and does not constantly recharge the battery, the absorption of electric energy by the electric motor remains high, causing the energy stored in the battery to be needed.
Current systems for reducing, or for monitoring, electric energy consumption of the electric motor have been developed.
A first solution is to turn off the electric motor anytime the control member is not used for steering. If the steering wheel is not moved, then a control unit turns off the electric motor such that it does not consume. However, turning on and off the electric motor causes an unpleasant sensation for the driver, since it does not allow a smooth driving, but the steering wheel has a “jerkily” behavior. Moreover, the turning on and off of the electric motor continuously in continuation leads to critical issues in the operation both from the electronic and mechanical standpoints.
A second solution is to keep the fluid within the steering circuit always under a constant pressure such to continuously provide the necessary increase in steering force, both whether the steering wheel is moved or not moved. Obviously this solution provides a smooth and constant driving sensation, but it has high electric energy consumptions. In order to reduce the high consumptions this solution reduces the revolutions of the electric motor each time the steering wheel is not moved, but nevertheless the absorption level remains high, and is excessive for the battery charge. Moreover, when the traveling conditions of the vehicle change in a sudden and continuos manner, the control reducing the revolutions of the electric motor does not have a prompt response, which is necessary to guarantee the correct operation of the system, with the risk of maintaining the number of revolutions of the electric motor always high in order to guarantee the necessary pressure level.
Therefore, there is an unsatisfied need for a servo-assisted steering device, which provides for low energy consumptions, independently of the running of the vehicle and while keeping a rotation and/or movement of the control member and which further provides, for a user, a behavior that is smooth and without jerks or jolts.